University of Chicago graduate student Forrest Gregg and Webitects developer Derek Eder launched a new online app that estimates which Chicago streets have been cleared of snow during a storm, as part of an effort to develop useful software using data provided by the city.

As a storm loomed the night of January 20, the two programmers created the app, called ClearStreets, in nine hours. ClearStreets improves upon the features of Plow Tracker, a separate app released by the City of Chicago on January 3 that tracks the location of snowplows in real time.

The app features a city map with dark lines representing road segments driven over by snowplows. With over 3,000 hits in the days following, the app has become immensely popular among Chicagoans.

However, the app’s creators warn, the website’s data may not exactly account for street conditions after a plow passes by. A snow plow may turn in between two points, making its location more difficult to pinpoint.

“I’m still working on improving it and making it more accurate,” Gregg said. “The biggest challenge is that when the plow goes around and takes turns, it is hard to guess where it has been going given just two locations.”

In order to plot the routes, Gregg and Eder used GPS location data from the snowplows, which was uploaded and updated online by the City of Chicago.

“The city was very easy to work with and did a great job of collaborating with us. We really want to thank the City for taking this innovative step toward open government,” Gregg said.

ClearStreets is one of four apps that make up the Open City project, a nonprofit civic organization that aims to develop helpful software based on open data provided by the City of Chicago. The group, which includes Eder, Gregg, and developers from Groupon and Webitects, has also launched Chicago Lobbyists, an app that documents the interactions between lobbyists and government officials, A Look at Cook to track Cook County spending, and Metra Schedules to follow transportation changes.